The present invention relates to testers for integrated circuit chips and particularly to the mounting of probe-cards of such a tester.
FIG. 1 shows a conventional installation for testing integrated circuit chips on wafers. This installation includes a tester which is capable of generating a plurality of test signals and measuring the responses of the tested chips to those signals. Tester is connected to a test head 12 held by a manipulator 14 and disposed above a wafer handling device 16, usually called a prober. Prober 16 comprises a wafer magazine (not shown) and a chuck 18 in which the wafers 20 to be tested are successively held. At the top of the prober and fixed to the frame thereof, a probe-card 22 is provided with downwardly extending probe-pins 24.
When a wafer 20 is being tested, the chuck 18 is moved so that the probe-pins 24 successively contact the pads of the chips on wafer 20. Thus, by bringing appropriate signals to some probe-pins 24 and by measuring voltages by means of other probe-pins 24 the operation of the chips can be checked.
At present, test signals can be of a very high frequency (about 300 Mhz). Accordingly, it is desired to reduce the length of the connections between the probe-pins 24 and test head 12 as much as possible in order to decrease the inductive effect of the connections. For this purpose, the probe-card 22 comprises connectors 26 including conductive pegs 27 connected to the probe-pins 24. The conductive pegs protrude from the top of the connectors and are mounted on springs. These pegs are intended to contact a test card 28 fixed at the bottom of the test head 12.
Such an installation has several drawbacks. Generally, it is necessary to provide a different probe-card 22 for each type of chip to be tested. Given the required positioning accuracy, it is difficult to mount and dismount the probe-cards. Moreover, for removing a probe-card, test head 12 has to be removed from prober 16. If the test head is removed too often, the conductive pegs 27 may be damaged and can no longer ensure satisfactory electrical contact.
It is thus an object of the invention to provide a probe-card that need not be entirely dismounted when the type of chip to be tested is changed.
Another object of the invention is to provide for simplified manipulation of probe-cards when the type of chip to be tested is changed.